1. Field of the Invention
The present invention relates to systems for harvesting biological material. More particularly, the present invention relates to a system for harvesting algae for use in continuous fermentation. Additionally, the present invention also relates to a system for fermentation using algae as the microorganism.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Research into efficient algal-oil production is currently being done in the private sector. Using algae to produce biodiesel may be a viable method by which to produce enough fuel to eliminate the dependence upon harvesting fossil fuels from non-sustainable resources. Algae require sunlight, carbon dioxide, small amounts of micronutrients, water, and small amounts of heat to grow. Given the proper conditions, some algae can double its mass in less than twelve (12) hours. Importantly, algae can produce a portion their biomass in the form of oil. Because the algae grows in an aqueous suspension, they are capable of producing large amounts of biomass and usable oil in either high rate algal ponds or photobioreactors. This oil can then be processed into usable fuel.
The algal industry is comprised of three major phases: growth, harvest, and utilization. Each phase requires different technologies to achieve economic viability. Each phase must become more efficient in order to support development and use of this sustainable resource. The difficulties in efficient and commercially viable biodiesel production from algae lie in establishing a reliable and resilient algal strain with a high lipid content and fast growth rate with a cost-effective cultivation system, such as a photobioreactor, that is optimized for that particular strain. This algal must also be amenable to harvesting without too much difficulty.
The growth phase is accomplished using technologies and media that are conducive to a specific algae species. Research has focused on algae growth for several years. Maximizing algae growth is one way of progressing towards commercially viable algal-oil production. The mass-production of oil by algae is mainly focused on microalgae; these organisms are capable of photosynthesis at less than 0.4 mm in diameter, including the diatoms and cyanobacteria. The macroalgae, like seaweed, have high availability, but the microalgae is less complex, grows faster, and contains a higher oil content in certain species.
Similarly, the utilization phase is accomplished using known and developing technologies for the processing of algal biomass and oils into usable fuel and materials. The applications are already known for using the algal-oil products. The demand for the biomass and oils currently surpasses the current industry's ability to supply.
The harvest phase is a key area of the algal-oil production field, requiring improvement before truly commercially viable production can be sustained. There are two major concerns for overcoming the lack of ability and technology to economically harvest the extract the oil and chemicals from the algae. First, since algae grows in an aqueous environment to optimal concentration levels of between 300 and 1500 ppm, large volumes of water must be pumped or transferred in order to harvest small amounts of dry algae. This hefty water requirement restricts the ability to scale up algal bioreactors to commercial levels. Second, extracting the oil and chemicals from the harvested algae currently requires uneconomical extraction methods, such as super critical CO2, ultrasonics, and solvent extraction. These restrictive limitations have so far inhibited true commercialization of algae to energy.
With regard to the large water requirement, open-pond systems were the first attempt at high volume cultivation of algae with high-oil content. These open system were flawed because of dependence upon resiliency of a particular algae strain in terms of temperature and pH and upon hardiness to compete against invading algae and bacteria. These single species systems were also vulnerable to viral infection. The open-pond systems required algal species with lower oil content because the algae had to divert energy and resources to proteins and carbohydrates to survive the environmental conditions. The high-oil content algal strain invests more resources into the production of oil, but they could not survive the conditions and had a slower growth rate.
The later focus on closed systems, not being exposed to open air, encountered a different problem. The closed system must located a cheap source of sterile carbon dioxide (CO2), and there have not been many cost-effective options. Although the possibility of placement near power plants to soak of pollution has been disclosed in the prior art.
With regard to the extraction methods, it has become a priority of large scale algal-cultivation system to looking for incorporating into existing infrastructures, such as coal power plants or sewage treatment facilities. This approach not only provides the raw materials for the system, such as CO2 and nutrients, but the connection converts those wastes into resources.
In the past, various patents have been issued in the field of fermentation, relating to processing bio-harvests. For example, U.S. Pat. No. 6,599,735, issued on Jul. 29, 2003 to the Bartok et al., describes fermentation assembly comprising a vessel for culturing living cells, at least two storage flasks in fluid communication with the vessel for supply of liquids and a first transport means for transferring the liquids from the storage flasks to the vessel, individual appliances operably connected to the transport means for monitoring the supply of the contents of the storage flasks to the vessel, a harvest flask in fluid communication with the vessel and a second transport means for transferring the fermentation broth from the vessel to the harvest flask, and a device operably connected to the first transport means for controlling and maintaining a constant dilution rate in the vessel with varying rates of individual supply of liquid from the storage flasks to the vessel.
U.S. Pat. No. 5,688,674, issued on Nov. 18, 1997 to Choi et al., describes a metabolite, e.g., ethanol, that is continuously produced from low cost carbohydrate substrates by a process which comprises pulverizing the carbohydrate substrate, liquefying and saccharifying the pulverized substrate, continuously fermenting the lique-saccharified substrate in a fermentor equipped with a moving filter, in the presence of flocculent biological cells maintained at a concentration ranging from 90 to 160 g/l by using the moving filter and a culture medium to produce a fermentation product mixture, and recovering the desired metabolite from the fermentation product mixture.
U.S. Pat. No. 4,069,149, issued on Jan. 17, 1978 to Jackson, describes a deep-tank reactor utilized for fermentation of waste liquid or other liquid in a biological reaction resulting in a solid cellular material. The resulting solid material, which is in suspension, is initially separated from the bulk of the liquid by a gaseous flotation process, using the dissolved gas in the liquid as the source of gaseous bubbles for flotation purposes.
U.S. Pat. No. 4,286,066, issued on Aug. 25, 1981 to Butler et al., describes an apparatus for continuously fermenting a moist particulate feed and distilling the fermentation product where a pressure-locked auger forces a moist particulate feed from a hopper into a fermentation tank. Liquor is removed from the tank, and solids are separated therefrom to produce a beer which is distilled in a distillation column. A combustion engine powers the auger and the means for separating solids, and the engine exhaust surrounds an inlet section of said auger to help heat the pressurized feed therein to produce fermentable sugar within the auger, and the auger includes a section passing to the tank in heat exchange relation to the distillation column to provide heat for distillation. The column is a multistage column angled to face the sun and has an upper glass plate to allow solar radiation to enter and penetrate between the foraminous plates of the column.
It is an object of the present invention to provide a system for continuous fermentation using algae.
It is another object of the present invention to eliminate the large volumes of water required for harvesting algae.
It is another object of the present invention to extract oil from harvested algae using an economical method.
It is yet another object of the present invention to provide an optimal reactor structure for any given set of operating conditions.
It is still another object of the present invention to provide concentrated algae for more efficient collection.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification.